Avalanche Forecast
Issued: Feb 25th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Deep Persistent Slabs.
rbuhler,
Avalanche Canada
Saturday night's storm is expected to form touchy new storm slabs and dangerous avalanche conditions are expected on Sunday. Conservative terrain selection is essential and it is recommended to avoid avalanche terrain in heavy snowfall areas of the region.
Summary
Confidence
Avalanche Summary
Many small to large (size 1 to 2.5) wind slabs were triggered naturally and by riders over the past few days. They mostly occurred on south to west aspects at alpine elevations resulting from northeasterly outflow winds. A few very large (size 3.5 to 4) deep persistent slab avalanches were also observed over the week, which likely occurred during very windy conditions.
Looking forward, the new snowfall and strong southwest wind are expected to form touchy new slabs, especially in wind-loaded terrain.
Snowpack Summary
Stormy conditions return, bringing substantial snowfall and strong southwest wind Saturday night. This new snow will bury the interface from the recent period of cold Arctic air which includes reports of surface faceting, small surface hoar in sheltered areas, and widespread wind-affected surfaces and wind slabs in exposed terrain at higher elevations resulting from the recent northeast outflow winds.
Prior to the storm, a small layer of surface hoar crystals could be found about 50 to 100 cm deep, particularly in areas sheltered from the wind around treeline. This layer appears to be gaining strength and is currently considered dormant, but could wake up in isolated areas from the weight of the new storm snow.
Large and weak facets that formed in November are found near the base of the snowpack. Although the likelihood of triggering this layer is low at this time, the consequence of doing so would be high. This layer is most likely to be human-triggered in thin, rocky slopes at alpine and upper treeline elevations.
Weather Summary
Saturday Night
Snowfall 15-35 cm, moderate to strong S-SW wind, treeline low around -18 °C.
Sunday
Snowfall 5-10 cm, light to moderate SW wind, treeline high around -12 °C.
Monday
Mainly cloudy with a chance of light flurries, light to moderate SW wind, treeline high around -12 °C.
Tuesday
Mainly cloudy with a chance of isolated flurries, light SE wind, treeline high around -9 °C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Avoid all avalanche terrain during periods of heavy snowfall.
- Use increased caution at all elevations. Storm snow is forming touchy slabs.
- Closely monitor how the new snow is bonding to the old surface.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
- Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
Problems
Storm Slabs
The new storm snow is expected to be most reactive in wind-loaded terrain, but deeper snowfall areas of the region may see a more widespread storm slab develop, especially where it might overlie a weakness that formed during the recent cold and dry period. Natural avalanche activity is expected overnight but could continue into the morning, and human-triggered avalanches are expected to be likely throughout the day.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Deep Persistent Slabs
A weak layer of facets exists near the base of the snowpack. The likelihood of human triggering is low given the layer's deep burial depth, but storm slab avalanches in motion have the potential to step down. Suspect terrain for human triggering includes steep, thin, shallow, and rocky terrain, which is often found near ridgelines.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Feb 26th, 2023 4:00PM
